This invention relates to a magnetic domain memory and more particularly to a memory in which a magnetic domain may be inserted into a position in a memory storage loop in the minimum amount of time after a magnetic domain previously in that position has been transferred out of that position.
Magnetic domain memories generally include one or more memory storage loops, each accommodating a number of magnetic domains and with each domain representing one bit of binary information. Each magnetic domain in a loop has a virtual position with respect to all other magnetic domains in the same loop. The magnetic domains are rotated around the loop in a controlled manner, so that a magnetic domain passes a particular point on the loop only periodically.
Prior magnetic domain memory systems have used one continuous path to move magnetic domains to and from the storage loops comprising the memory. In one such system, a closed continuous path is used with a bidirectional transfer gate for each loop for moving the magnetic domains between the stoage loop and the path. Because the magnetic domain positions pass this gate only once per revolution about the loop, two revolutions are necessary between each retrieval of a magnetic domain since after the first magnetic domain is retrieved or transferred out of the loop a new one must be put in its old position before a second retrieval can occur. Where the same bit information is required repeatedly these relatively long time periods betweem successive retrievals substantially increase the operational time required to perform such functions.
A second type organization designed to speed up the storage of magnetic domains has an unclosed path which passes each memory storage loop at two points. At each of these points there is a one-way gate connecting the storage loop and the path. One gate transfers magnetic domains into the storage loop, while the other transfers the domains out of the storage loop. Since magnetic domains are now moved into and out of the storage loops at separate points, the access to a magnetic domain position depends on how many times the virtual position of the magnetic domain has to move around the loop from the output point to the input point before the new magnetic domain, moving along the path, will be at the input transfer point. Presently, a minimum of one and one-half revolutions of the virtual position from the output to the input transfer point is required. This is because of the length of the path. Thus, in this arrangement as in the one first discussed above, there can be no continuous transfer of magnetic domains into and out of the memory storage loop positions. Rather, there is still a substantial time interval between transfers into and out of the same virtual position in the storage loop.